2.0 Analysis 2.1 Introduction The aircraft was determined to have been serviceable for the flight and there was no indication of impairment in crew performance. Consequently, the analysis will deal with the following factors: weather information available to the crew, crew decision making, crew information and preparedness, and aerodrome information at St. John's. 2.2 Weather Information Approximately seven minutes before the accident, the flight crew received the latest surface wind conditions at the airport which indicated the wind speed to be 15 to 25 knots estimated. The wind speed was estimated due to the fact that the wind speed indicator at the airport was unserviceable. According to the aerodrome forecast, the wind speed was expected to be 25 knots gusting to 35 knots. The area forecast indicated wind speeds of as much as 25 to 35 knots gusting to 50 knots. Based on the forecasts and the conditions encountered on approach, it is probable that the wind encountered on approach was much stronger than that which was reported to the flight crew. The forecast and actual weather conditions at St. John's were conducive to turbulence, wind shear, and downdrafts. 2.3 Crew Decision Making The flight crew members decided to continue to their destination after they were advised that the weather was going to be below the landing minima for the only available approach. This decision was based on a PIREP relayed from an aircraft which landed safely approximately 18 minutes before the accident; the PIREP had given no indication of turbulence. On the approach, the crew was not concerned with the presence of the moderate turbulence during the initial stages because they had flown into St. John's several times in the previous week and encountered similar conditions. However, they were not prepared for the presence of the wind shear and the severe downdraft which followed. 2.4 Crew Information and Preparedness The predominance of information regarding severe downdrafts is generally associated with thunderstorms or mountainous regions. Flight crews are provided with information, strategies, and/or training for managing their flights safely when such conditions may be encountered. However, available awareness training or information is limited for the circumstances which this crew faced in St. John's; no thunderstorms were present, and the terrain is not generally considered to be mountainous. The only weather advisory existed on the approach plates, and it provides a warning of turbulence in strong wind conditions. The fundamental strategy for operating safely in conditions where severe weather exists is avoidance. This strategy can only be implemented if the crew has the correct information for the area in which the flight will be conducted. The FA included in the weather package that the crew had received prior to departure was not the correct forecast for the St. John's area and only forecasted light to nil turbulence. The crew response and recovery action when the downdraft occurred were considered appropriate. 2.5 Aerodrome Information The only advisory of the presence of potentially adverse conditions on approach to St. John's Airport is provided on the approach plates. A cautionary note warns pilots that they may anticipate moderate to severe turbulence; however, in previous issues of the charts, pilots were advised that dangerous downdrafts could exist on the approaches. The more appropriate warning is that which advises of the potential for dangerous downdrafts. Pilots who approach the St. Johns's Airport under visual flight rules (VFR) may not have reference to the instrument approach procedure charts. As there is no mention of turbulence in the CFS, VFR pilots may be unaware of turbulence hazards around the airport. Section 323 of TP 308, Criteria for the Development of Instrument Procedures, would allow for an increase in the intermediate approach altitude and FAF crossing altitude for runway 16. This increase in the minimum altitude would help to position aircraft above downdrafts and would help to limit the amount of time that aircraft would be exposed to the hazards associated with lee-side phenomena associated with precipitous terrain. It would also provide the aircraft with more terrain clearance in the event of an inadvertent encounter with a downdraft; the altitude could be increased from the present 1600 feet to as much as 1900 feet. Had this buffer been applied, it is possible that the aircraft would not have struck the trees. 3.0 Conclusions 3.1 Findings as to Causes and Contributing Factors The weather conditions on the approach at St. John's Airport were conducive to severe turbulence, wind shear, and downdrafts. The aircraft encountered severe turbulence and downdrafts which caused a sudden loss of altitude and subsequent impact with the trees. The pilot applied the correct wind shear recovery techniques. 3.2 Other Findings The flight crew members were certified, qualified, and trained to operate the aircraft in accordance with existing regulations. The weight and centre of gravity of the aircraft were within the prescribed limits. The cautionary note warning of downdrafts in the instrument approach procedures charts for St. John's airport was removed. The listing for the St. John's Airport in the CFS did not contain information which warns of the existence of severe turbulence, wind shear, and downdrafts. The obstacle clearance altitude on the intermediate approach does not take into account the precipitous terrain criteria contained in TP 308, Criteria for the Development of Instrument Procedures. 4.0 Safety Action 4.1 Action Taken 4.1.1 Safety Memo Within days after the accident, the operator issued a safety memo to all company personnel informing them of the circumstances surrounding the accident and the potential wind shear hazard at St. John's. 4.1.2 Aviation Safety Advisories Two aviation safety advisories have been sent to TC. One advisory has identified the absence of consideration for the wind conditions and precipitous terrain at St. John's in obstacle clearance height determination. The other advisory identified the inadequacy of pilot information regarding the potential hazardous weather/wind conditions. Both advisories suggested that these circumstances could be present at other airports in Canada. In its response to the advisories, TC indicated that both TC and NAV CANADA concur with the subject of the advisories. Furthermore, NAV CANADA has indicated to TC that on the Publication of Turbulence Advisories, they will implement procedures to ensure that information is available to pilots regarding potential hazardous weather/wind conditions; on the Obstacle Clearance Criteria - Precipitous Terrain advisory, NAV CANADA has indicated to TC that they will examine the modalities of its application at St. John's. 4.1.3 Cautionary Information After being informed of the lack of information on turbulence, windshear, and downdrafts in the CFS, NAV CANADA is initiating action to include this information in the CFS. TC is also advising the regional managers of Aerodrome Safety to be vigilant in ensuring that relevant cautionary notes on approach plates are also provided in the appropriate sections of the CFS.